Differences in rates of diapause induction are thought to produce differences in the distribution of flies. Therefore, we investigated differences in the day length for entering diapause and effective chill treatment for termination of pupal diapause in Parasarcophaga similis and Boettcherisca peregrina flies found in Japan. Results showed maximum rates of diapause incidence for P. similis colonies from Sapporo, Tokyo and Nagasaki were 98% under 13L : 11D at 20°C, 100% under 11L : 13D and 80% under 10L : 14D, respectively. Diapause incidences for B. peregrina colonies from Tokyo and Nagasaki were 100% and 98% under 13L : 11D at 20°C. Emergence rates for diapausing pupae of P. similis (Sapporo) chilled at 4°C then transferred to diapause-terminating conditions at 27°C (16L : 8D) or 20°C (11L : 13D) were 65% and 80%. In B. peregrina (Tokyo), chill treatment was effective for 89% emergence. Adult P. similis (Sapporo) flies emerging from pupae that experienced chill treatment laid larvae that entered diapause at an incidence of 99.5%, whereas adult B. peregrina (Tokyo) laid 22% larvae destined for diapause. These flesh flies appear to move into new environments by successfully developing the ability to emerge at lower temperatures and possibly avoiding the maternal effect.

The attractive baited lethal ovitrap, an autocidal ovitrap, is an alternative tool to control mosquitoes by attracting ovipositing females to lay their eggs in artificial containers. Ovitrap attracts female mosquitoes by biotic factors, such as larval food and conspecific larvae. Long-lasting matrix-release formulations containing 2% pyriproxyfen, SumiLarv®2MR, are less harmful to the environment and can effectively reduce targeted mosquitoes for at least six months. We examined the effects of SumiLarv®2MR on attraction of Aedes aegypti (L.) and Ae. albopictus (Skuse) to biotic factors, such as larval food and conspecific larvae, by two-choice tests. For both species, no significant difference arose between water containing SumiLarv®2MR and water alone. Both species laid more eggs in cups with larval food prepared two days before, and the attraction to the food was not affected by pyriproxyfen. Conspecific larvae of both species did not show attraction clearly but pyriproxyfen might increase attraction to conspecifics in Ae. albopictus. SumiLarv®2MR did not deter gravid females of both species and did not reduce the effects of the larval food, suggesting that SumiLarv®2MR is a promising formulation for lethal ovitraps.

The emergence of pyrethroid resistance in Phlebotomus sandflies is an urgent issue for vector control using indoor residual spraying (IRS). Two amino acid substitutions at codon 1014 (L1014F and L1014S) in the voltage-gated sodium channel (VGSC) gene have been reported in Phlebotomus argentipes, a major vector of visceral leishmaniasis (VL). Known as “knockdown resistance (kdr),” these substitutions confer pyrethroid resistance in various insect species. The frequency of the VGSC mutant allele was investigated in Phlebotomus and Sergentomyia species at two different IRS regimes: “long-term treated,” 12 rounds for seven years in Mymensingh, Bangladesh; “short-term treated,” four rounds for two years in Pabna, Bangladesh. In Mymensingh, the L1014F/S allele frequency was 100% in P. argentipes and 98% in S. babu babu. In Pabna, the frequency was 41% in P. argentipes. At other kdr sites (codons 1011, 1016, and 1020), the genotypes of all specimens in Bangladesh were wild-type homozygotes. This study showed that a long and frequent exposure to IRS is crucial for the development of genetic mutations in VGSCs, a higher kdr frequency, and pyrethroid resistance in Phlebotomus.

Thirty years have passed since the last surveillance of the mosquito fauna on the entire Chichi-jima, Ogasawara Islands, Japan. Herein, we report the results of a mosquito study conducted on the Ogasawara Islands in 2015 and 2017. In this study, 2,371 individuals belonging to seven species in three genera were collected, including 262 mosquitoes belonging to five species in three genera collected in 2015 and 2,109 specimens representing six species in three genera obtained in 2017. The dominant species in dry-ice trap collections were Culex boninensis and Cx. quinquefasciatus, and the latter was dominant in yeast trap collections. Aedes albopictus, Ae. savoryi, and Cx. boninensis were dominant in sweep net collections, while Ae. albopictus and Cx. quinquefasciatus were dominant in the larval collection. Culex boninensis and Ae. albopictus were widely distributed on the islands. Gene sequences of cytochrome c oxidase subunit I from 55 specimens belonging to the seven species in the three genera, including four endemic species (Ae. wadai, Ae. savoryi, Cx. boninensis, and Lutzia shinonagai), were registered in GenBank. Genetic distance analysis showed low intraspecific variations and low mean genetic distances (between 0.0% and 0.8%), indicating significant homogeneity among mosquito populations on the Ogasawara Islands.

Vector control is crucial for mitigation of mosquito-borne diseases such as malaria. The emergence of insecticide resistance has begun to hamper vector control in recent years. Novel vector control strategies that do not depend on chemical insecticides are needed. We evaluated the potential of venoms, the poisonous secretion of the animals, as sources of novel mosquitocidal molecules. We screened for mosquitocidal effects of seven venoms, using Melittin (Mel) as a positive control by microinjection using the malaria vector Anopheles stephensi mosquitoes. Tf2, Hm3a (Hm3), Chlorotoxin (Ctx) and Mel caused significantly high mortality among these mosquitoes. To identify the most effective venom, we assayed for the lowest effective dose of Tf2, Hm3, Ctx, and Mel. Tf2 displayed the highest mosquitocidal potency. We next determined the LD₅₀ of Tf2 against An. stephensi mosquitoes. The LD₅₀ of Tf2 against An. stephensi was 5.9×10⁻¹³ mol/mosquito. Our results indicated that Tf2 was the most effective candidate venom molecule for a novel vector control agent. Further research regarding Tf2 is expected to contribute to the control of mosquito-borne diseases such as malaria.